1. Field of the Invention
The present invention relates to an off-line teaching method which makes it possible to accurately estimate the amount of correction of teaching data previously obtained by instructing a logical robot model by using an off-line teaching apparatus.
2. Description of the Related Art
Recently, in order to apply the robot to various workings, in general, a variety of tools are attached to the face plate of the robot arm to allow the robot to perform working.
A large number of techniques for instructing the robot as well as a large number of techniques for making various types of correction for the instruction data have been hitherto suggested. For example, a method has been suggested in relation to the instruction technique for the robot (see Japanese Laid-Open Patent Publication No. 5-27828), in which information necessary for the robot working to be used is given in conformity with the request of a user as accurately as possible, and the burden for the user is mitigated as less as possible.
In relation to the technique for correcting the instruction data, the following methods have been suggested, including, for example, a method in which the revision for the instructed point and the correction for the instructed locus can be easily executed under the same operation condition as that used during playback even at a place separated from the working job site so that the burden for the operator to perform the operation for revising the instruction is mitigated (see Japanese Laid-Open Patent Publication No. 8-286726); a method in which the positional discrepancy can be automatically corrected for all striking positions with a high degree of accuracy (see Japanese Laid-Open Patent Publication No. 7-325611); a method in which the position of the robot is corrected by using a neural network (see Japanese Laid-Open Patent Publication No. 6-114769); a method in which the revising operation sensuously comprehensible for the operator can be performed when the conversion data for the robot operation is revised upon occurrence of malfunction in the operation range concerning the revised instruction data (see Japanese Laid-Open Patent Publication No. 5-289730); a method in which the repeated logical operation based on the modified Powel method is applied for respective elements of unknown variable matrix and constant matrix to ensure the absolute positional accuracy of an arm-type multi-joint robot by using only the angle of rotation of the arm axis while avoiding the measurement on the rectangular coordinate in order to further improve the accuracy and increase the computing speed (see Japanese Laid-Open Patent Publication No. 6-274213); and a method in which the setting error of a certain constant and the setting error of tool offset are automatically corrected by using setting data for a robot of the multi-joint type attached with a tool at its wrist (see Japanese Patent No. 2520324).
In relation to the setting of the tool cusp point, a method has been suggested (see Japanese Laid-Open Patent Publication No. 7-191738), in which the tool cusp point can be set for a desired attitude in accordance with a simple procedure by utilizing a simple setting jig even when the design data is not available. A method, which is based on the use of CAD data, has been suggested (see Japanese Laid-Open Patent Publication No. 8-286722), in which it is unnecessary for the operator to thoroughly input the initial setting data, the working procedure data, and the working operation data one by one so that the amount of input to be performed by the operator is greatly decreased. A method, which relates to presentation of locus, has been suggested (see Japanese Laid-Open Patent Publication No. 8-174454), in which the relative positional relationship between a workpiece and an actual position of an actually operating tool can be easily and accurately recognized when a workpiece is retracted from the working position.
However, in the illustrative conventional techniques concerning the off-line teaching described above, the working point of the robot is subjected to positional adjustment with a high degree of accuracy by using the attitude which differs as far as possible, with respect to the fixed point in the space at the working site at which the actual robot is installed. Moreover, the attitude has been arbitrarily determined by the judgement of the operator.
As described above, the conventional technique entrusts the judgement of the individual operator. Therefore, an inconvenience arises in that it is not necessarily possible to obtain the teaching data which is appropriate to calculate the correction amount. Further, a problem arises in that the conventional technique requires a long time, because the attitude is thought of at the working site.